Q345R受火后力学性能及组织的变化

Evolution of Mechanical Properties and Microstructure of Q345R Steel after Fire Exposure

通过对Q345R材料在不同受火温度、保温时长及冷却方式条件下进行热处理来模拟其受火损伤的热暴露试验,进一步评定材料的力学性能及相应的微观组织.研究表明:在20℃~649℃受火温度下,材料力学性能均满足要求,732℃~816℃受火温度下,与空冷条件下相比,水冷对其力学性能影响较大;受火温度低于649℃时,材料组织为铁素体+珠光体,高于649℃时,金相组织明显发生变化,水冷下晶粒度与空冷条件下相比较为不均匀;热处理温度不高于649℃时,材料无明显脱碳现象,在816℃时材料表面脱碳层最大深度约0.20 mm;随着受火温度的升高,热处理后表面颜色呈红褐色、灰褐色、暗红、亮红色变化.

Heat treatment experiments were conducted on Q345 R steel under different fire temperatures,insulation durations and cooling treatment,which could reflect the influence of fire on the material.Hence the mechanical properties and corresponding microstructure of the material were further evaluated.It is found that at the fire temperature of 20℃~649℃,the mechanical properties of the material can meet the requirements of application.If the fire temperature rises to 732℃~816℃,compared with the air cooling,water cooling can affect the mechanical properties of the material more.When the fire temperature is lower than 649℃,the microstructure of the material is ferrite and pearlite,however,when the temperature is higher than 649℃,the metallographic structure changes significantly.The grain size by water cooling is less uniform than that by air cooling.There is no obvious decarburization when the heat treatment temperature is lower than 649℃.However,the maximum depth of decarburization layer on the surface of the material will be approximately 0.20 mm when the temperature reaches 816℃.As the fire temperature increases,the surface color of the heat treatment becomes from reddish brown,to taupe,to dark red and to bright red at last.